For those of you who have not understood my question. In one line , I have to do a data migration and have to find the child who have multiple parents. So wherever you have multiple parents then assign a new id to the child.

eg;

childid childname parentid

100 abc 200

100 abc 300

desired output

childid childname parentid

100 abc 200

101 abc 300

I hope now this will be clear. And I am doing this for historical data so query ll be quite complicated.